Gorin



Aug. 21, 195

Original Filed Sept. 13, 1949 E. GO CRYSTALLINE COMPLEXES OF' UREA AND STRAIGHT RIN '2,759,919

CHAIN ALKYL MONOHALIDES 2 Sheets-Sheet l .i lNVENroR bef-eff 6011 ug- 21, 1956 GoRlN 2,759,919

E CRYSTALLINE COMPLEXES OF UREA AND STRAIGHT CHAIN ALKYL MONOHALIDES United States Patent Office 2,759,919 Patented Aug. 21, 1956 CRYSTALLINE COMPLEXES F UREA STRAIGHT CHAIN ALKYL MONOH-ALIDES Everett Gorin, Pittsburgh, Pa., assigner `to `Socony Mobil Oil Company, Inc., a corporation of New York Continuation of `application Serial No. 115,511, September 13, 1949. This application August 17, 1953, Serial No. 374,707

Claims. (Cl. 260-96.5)

This invention has to do with the separation of hydrocarbons and hydrocarbon derivatives -of different molecular configuration from mixtures containing the same, and also has to do with the lpreparation -of `new and novel compositions.

This application is a continuation of application Serial No. 115,511, filed September 13, 1949, now abandoned, which, in turn, is a continuation-impart of application Serial No. 4,997, led January 29., 1948, now abandoned.

I. FIELD OF INVENTION Numerous yprocesses have been developed for the separation of hydrocarbons and hydrocarbon derivatives of different molecular configuration by .taking ladvantage of their selective solubility in selected reagents or solvents from which they may later be separated. Exemplary of hydrocarbon separation procedures is the Edeleanu process, wherein paranic materials are separated from aromatics by virtue of the greater solubility of aromatics in liquid sulfur dioxide. Lubricant oil solvent refining processes, solvent deasphalting, solvent dewaxing and the like are further -examples of the separation of hydrocarbons of different molecular configuration. Typical of selective solvent procedures for separating hydrocarbon derivatives is the separation of parafn Wax, rnonochlorwax and polychlorwaxes, with acetone as the selective solvent.

This invention is concerned with the general field 'outlined above, but based upon a different and little-known phenomenon, namely, the differing ability of hydrocarbons and hydrocarbon derivatives to enter 'liuto and to `be removed from certain crystalline complexes. As used herein, the term complex broadly denotes a combination of two or more compounds.

rIhis invention is predicated upon the knowledge that urea forms complex crystalline compounds to `a varying degree with various forms lof hydrocarbons and hydrocarbon derivatives.

II. PRIOR ART For some years it has been known that various isomers of aromatic hydrocarbon derivatives form complexes with urea. Kremann (Monatshefte f. Chemie 28, 1125 (1907)) observed that complexes, designated as double compounds, of urea and the isomeric cresols are stable at different temperatures. Schotte and Priewe (1,830,- 859) later separated meta-cresci yfrom the corresponding para isomer by selectively forming a meta-cresol-urea complex, which was described as an addition compound; the latter compound was separated from the para isomer and then split up by distillation or with Water or acid to obtain pure meta-cresol. The addition compound of .meta-cresol and urea was `shown thereafter to have utility as a disinfectant (Prisme-4,933,757). Bent- `ley and Catlow (1,980,901) found a number of aromatic amines containing at least one basic amino group capable of forming double compounds with certain isomeric phenols. It has also been shown that trans-oestradiol can be separated from the corresponding cis-compound by forming a diiiicultly lsoluble compound -of urea and transoestradiol (PrieWe-2,300,-134).

The forces between urea .and the compounds of the foregoing complexes are due to specific chemical interaction between the various functional groups.

One heterocyclic compound, 2:6 lutidine, has been found to form a crystalline compound with urea, thus affording a means of separating the lutidine from betaand gamma-picolines (Riethof 2,295,606).

Comparatively few aliphatic hydrocarbon derivatives have been known to date to form complex compounds with urea. In German vpatent Iapplication B 190,197, IV d/ 12 (Technical Oil Mission, Reel 143; Library of Congress, May 22, 1946), Bengen -described a method for the separation of aliphatic oxygen-containing compounds (acids, alcohols, aldehydes, esters and ketones) and of straight chain Vhydrocarbons of at least six carbon atoms from mixtures containing the same, the method being predicated upon the ability of such compounds and hydrocarbons to form Additions-Produkt with urea. In the Technical Oil Mission translation of the Bengen application, however, the urea complexes were designated adducts,` which term apparently stems 4from the anglicized addition product.

III. DEFINITIONS From the foregoing discussion of prior art (II), it will be clear that a variety of terms have been applied to urea complexes. The latter have been rather loosely described as double compounds, addition compounds, diicultly soluble compounds, Additions-Produkt, and adducts All of these terms are somewhat ambiguous in that they have also been used to describe products or complexes of different character than the urea complexes under consideration. This is particularly so with the term adduc, and the related 'term unadducted Inaterial. While the term adduct is simple and convenient, is `an unfortunate designation, inasmuch as Vit confuses these complexes with other substances known in the chemical art, Specifically, adduct has been applied to Diels-.Alder reaction products, formed by reaction 'of conjugated diolefins and oleins and their derivatives. As is well known, Diels-Alder products, as a rule do not revert to their original constituents when heated or treated with water, acids, solvents, etc. Moreover, the term adduct has `been defined earlier as The product of a reaction between molecules, which occurs in such a way that the original molecules -or their residues have their long axes parallel to one another. (Concise Chemical and Technical Dictionary.) Further ambiguity is introduced by the term adduction, which has been defined as oxidationl (I-Iackh) To avoid the foregoing coniiicting terminology, several related terms have been coined to define with greater specificity the substances `involved in the phenomenon under consideration. As contemplated herein and as used throughout the specification and appended claims, the following terms identify the phenomenon:

Plexad-a revertable associated complex comprising a plexor, 'such as urea, and at least lone other compound; said plexad characterized by reverting or decomposing, under 4the iniiuence of hea't and/or various solvents, to its original constituents, namely, a plexor and at least one plexand.

PleXand--a compound capable of forming a plexad with a plexor, such as urea; compounds of this character differ in their capacity to form plexads, depending upon various factors described hereinafter;

Antiplex-a compound incapable of forming a plexad with a plexor.

Plexor-a compound capable of forming a plexad with a plexand; such as urea.

Plexate-to form a plexad.

Plexation-the act, process or effect of plexating.

IV. OUTLINE OF INVENTION It has now been discovered that certain terminallysubstituted straight chain compounds, plexands, form plexads with urea. It has also been discovered that, by selective plexation with urea, a terminally-substituted straight chain compound can be separated, in the forn of a plexad, from a mixture containing the same and a non-terminally-substituted compound. This separation procedure is effective also when the paraffin derivatives have the same number of carbon atoms, as in the case of isomers, or have a different number of carbon atoms. Selective plexation is also effective when the terminal and non-terminal substituents are different, and the num ber of carbon atoms of the substituted paraflins are the same or diffrent.

The substituent groups which may characterize the terminally-substituted compounds are inorganic and organic groups of the following character:

(a) Halogen: F, Cl, Br and I',

(b) Nitrogen-containing: NH2, NH(R), NRz, NO2, NOH, CN, CONH2, CONH(R), CON(R)2, CNO, CNS, NCO, NCS, etc., wherein R is a hydrocarbon radical;

(c) Sulfur-containing: SH, SR, SOaH, OSOsH, SOzI-I,

SOzR, wherein R is a hydrocarbon radical, SOzZ wherein Z is a halogen atom, or group such as hydrocarbon, hetero, etc.

(d) Cyclic: Cycloalkyl such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, chlorcyclohexyl, etc.; aryl such as phenyl and chlorphenyl; hetero such as thienyl C4H3S, fuxyl C4H30, pyrryl, C4H4N, pyridyl C5H4N, thiazyl CsHzNS, pyrazolyl CsHaNz, piperydyl CsHroN, etc.;

(e) Alkenyl: methylene, vinyl, etc.;

(f) Haloalkyl: dichlormethyl Cl2CH-, etc.

As `contemplated herein, the invention makes possible the separation of one or more plexands from a mixture containing the same, such plexand or plexands being separated in the form of a plexad or plexads which, as described in detail hereinbelow, revert to the plexor, urea, and the plexand or plexands under certain conditions. The separation, therefore, is an excellent means for obtaining, in pure or concentrated form, one or more plexands or antiplexes whichever is the desired material. The invention also provides a means of forming new compositions of matter, namely, a number of plexads which may be used as a source of a plexor, urea, or as a source of a plexand.

V. OBI ECTS It is an object of this invention, therefore, to provide an effective means for separating hydrocarbons and hydrocarbon derivatives of different molecular configuration from mixtures containing the same.

It is also an object of this invention to selectively separate terminally-substituted straight chain compounds from mixtures containing the same.

A further object is to separate a terminally-substituted straight chain compound from a mixture containing the same and a non-terminally substituted isomer.

Still another object is to separate a terminally-substituted straight chain compound from a mixture containing the same and a non-terminally-substituted straight chain compound having a different number of carbon atoms.

An additional object is to separate a terminally-substituted straight chain compound from a non-terminally substituted compound, wherein the substituents are different and the number of carbon atoms of the respective compounds are the same. A related object is to separate a terminally-substituted straight chain compound from a non-terminally-substituted compound, wherein the substituents are diiferent and the number of carbon atoms of the respective compounds are different.

A further object is to separate a non-terminally substituted compound from a mixture containing the same and a second non-terminally substituted compound less susceptible to plexation.

Another important object is the provision of a continuous method of separation of said plexands and antiplexes, which method is flexible, capable of relatively sharp separation, and not highly demanding of attention and of utilities such as heat, refrigeration, pumping power, and the like.

An additional object is to provide a plexand or plexands substantially free of an antiplex or antiplexes. A corresponding object is the provision of an antiplex or antiplexes substantially free of said plexand or plexands.

Another object is to provide a new and novel class or sub-classes of plexands comprising a plexand and urea. A related object is the provision of a new and novel class or sub-classes of plexads comprising a secondary plexand and urea.

Other objects and advantages of the invention will be apparent from the following description.

VI. INVENTION IN DETAIL As indicated above, it has been found that the foregoing objects are achieved by plexation with urea (a plexor) of a plexand or plexands.

(1 Plexands Plexands contemplated herein are represented by the general Formula A:

(A) X(CH2)n.CH3

wherein n is a whole number and wherein X is a substituent group of the character described above, with n and X being interrelated.

The substituent group X may be any of the types outlined above subject, however, to one important restriction, namely, that of geometrical size. Two dimensions are of importance in determining the nature of the separation that may be obtained between compounds-plexands and antiplexes-given above. The first dimension is the crosssection of the group (X) taken in a direction perpendicular to the bond joining the group (X) to the parent hydrocarbon. This distance-widt -is taken at the widest portion of the group and may be conveniently given a quantitative measure as the distance from between outer covalent radii of the two most widely separated atoms along the cross-section of the group where the covalent radii are those given by Pauling (Pauling-Nature of the Chemical Bond; Cornell University Press; Ithaca, N. Y.; 1939). The second distance-length-is the projection along the bond joining the group to the parent hydrocarbon of the distance from the center of the carbon atom to which the group is attached, to the center of the atom whose covalent radius shell extends furthest in the direction of said bond, plus the covalent radius of said bond.

The rst distance determines the length of the aliphatic chain required to obtain plexation at room temperature (25 C.) with a saturated urea solution, a plexor, when the group (X) in question is attached to the terminal car bon atom of the aliphatic chain. In the case of composite groups of the type -COY, -CHzCOY and -CH2Y, where Y is a non-aliphatic radical such as chlorine or amino, the =CO, -CHzCO and -CH2 constituents, respectively, are considered as part of the aliphatic chain and the width computed is that for the radical Y.

The widths of a number of typical groups computed according to the method given above are listed in order of size in Table I below:

TABLE I.-WIDTH OF VARIOUS G'ROUPS IN A 1. 20 2. 67 l. 28 3. 32 1. 98 3. 69 l. 98 4. 38 2. 11 4. 74 2. 1l Phenyl 5. 15 2.28 2 or 3 Methyl Cyclo- 5. 49 2. 66 hexyl.

O- or M-tolyl 6. 09

The correlation between the widt of the group and the length of the aliphatic chain required for plexad formation at room temperature is an approximate one. This relationship depends to some extent upon the nature of the group (X) as well as upon the width of the group (X). For example, in the case where two groups (X) are the same size, the group which imparts a higher melting point to the substituted parain will form the stronger plexad, i. e., will form a plexad when the aliphatic chain is somewhat shorter in length.

Only the carbon atoms in the chain are considered to contribute to the chain length, that is atoms such as oxygen, sulfur, nitrogen, etc., are not included in the atom total. Accordingly, then, the straight chain compounds contemplated herein include straight chain aliphatic hydrocarbons and straight chain aliphatic hydrocarbons in which one or more of the carbon atoms of the chain have been replaced by such atoms as oxygen, sulfur, nitrogen, and the like.

It is possible, however, to give the unequivocal limits for the relation between width of the group (X) and size of the carbon chain required for plexation with urea at room temperature, 25 C. These limits are set forth in Table II below:

TABLE II.-CORRELATION BETWEEN lGROUP (X) AND MINIMUM CHAIN UREA PLEXATION AT 25 C.

WIDTH OF LENGTH FOR Minimum hain Length,

Number of Carbon Atoms Group It is to be understood that these limits apply for plexation at temperatures of the order of about 25 C. The minimum number of carbon atoms in the chain is generally lower for plexation at lower temperatures, but generally not more than one or two carbon atoms lower. In the same vein, for an increase in temperature, a correspondingly higher number of carbon atoms will be required in the carbon chain.

By way of illustration, the following compounds are typical plexands:

(a) Halogen compounds: n-heptyl fluoride, n-heptyl bromide, n-octyl chloride, n-octyl bromide, n-hexadecyl chloride, n-hexadecyl bromide, n-octadecyl chloride, noctadecyl bromide; etc.

(b) Nitrogen-containing compounds:

Amino--n-octylamine; n-decyl amine; n-hexadecyl amine; n-octadecyl amine; n-octadecenyl amine; methyl, n-octyl amine; butyl, .n-octyl amine; phenyl, n-decylamine; etc.

Cyano-nhexy1 nitrile; n-octyl nitrile; n-tetradecyl nitrile; n-octadecyl nitrile; etc.

Nitro-l-nitro-n-decane; 1nitrondodecane; l-nitron-octadecane; etc.

Amido-n-octanamide; n-dodecanamide; n-octadeca'namide; n-octadecenamide; N-methyl, n-octanamide; N-hexyl, n-decanamide; N-phenyl, n-decanamide; etc.

Cyanate and isocyanate-n-hexyl cyanate; n-hexyl isocyanate; n-decyl cyanate; n-decyl isocyanate; nhexadecyl cyanate; n-hexadecyl isocyanate; etc.

Thiocyanate and isothiocyanate-n-hexyl thiocyanate; n-hexyl isothiocyanate; n-decyl thiocyanate; ndecyl isothiocyanate; n-octadecyl thiocyanate; noctadecyl isothiocyanate; etc.

(c) Sulfur-containing compounds:

Mercapto-n-octyl mercaptan; n-dodecyl mercaptan; n-hexadecyl mercaptan; n-octadecenyl mercaptan; etc.

Suldo (SR)-methyl, n-octyl sulfide; butyl, n-dodecyl sulfide; amyl, n-hexadecyl sulfide; etc.

Sulfato-n-dodecyl sulfate; n-hexadecyl sulfate; etc.

Sulfonyl halide-n-decyl sulfonyl chloride; n-dodecyl sulfonyl bromide; n-hexadecyl sulfonyl iodide; etc.

(d) Cyclic substituent: 1-cyclopropyl-n-octadecane; lcyclohexyl-n-hexadecane; l-phenyl-n-octadecane; lthienyl-n-octadecane; etc.

It is to be understood that terminally-substituted straight chain compounds containing a second terminal substituent on the opposite terminal carbon atom, are also contemplated herein as plexands. Such disubstituted compounds are also subject to approximately the foregoing relationships of terminal group width and chain length. Compounds of this character are represented by the following general formula:

wherein n is a whole number, and X and X are the same or different and as deiined above.

Illustrative of such compounds are:

1,10-dich1or-n-decane; 1,8-n-octane diamine; 1,10-n-decane diamide; 1,12-n-dodecane dithiol; 1,18-disulfo-n-octadecane; etc.

Another class yof compounds contemplated herein as plexands are those having a non-terminal substituent, and being represented by general Formula B:

wherein r and m are integers, the sum of which is equal to n-2, and n and X are as defined above.

The 1ength, rather than the width, of the substituent group (X) roughly determines the minimum carbon chain length required for plexation of the foregoing plexands (B) namely, non-terminally substituted straight chain compounds. These compounds may be considered secondary plexands. The minimum chain length is also to some extent a function of the position substituted as well as of the chemical nature of the group. Thus, in compounds of this type, the minimum chain length required for plexation is determined by the length of group HaC(CH2)1-, if r is small enough so that this alkyl group is shorter in length than the substituent group (X). It is possible, bearing this relationship in mind however, also to give` rather wide lirnits in the correlation of group length with the minimum chain length required for plexation. The lengths of various groups are given in Table III, below, while the correlation of chain lengths with group lengths is given in Table IV, also provided below:

TAB LE III.

2. O6 -CHzCl 3.11 2, 17 CN s. 25 2. 61 3. 37 2. 76 3. 43

2. -cyclohexyl (average conguration) 5. 09 -Br 3. 05 -phenyl 5. 69

TABLE' I`V;-CORRELATION BETWEEN LENGTH OF NON-TERMINALLY-SUBSTITUTED GROUPS-AND MINI- grS/SllglCLEYGCLHQv REQUIRED FOR UBEA PLEXA- Minimum Chain Group "L ength Length,

(in A)' Number of Carbon Atoms It is to be understood', once agan, that the limits shownpin Tablev IV apply for plexation at temperatures of about 25 C. Here toot,- the minimum number of carbon atoms in the chainr is somewhat lower for plexation at; lower temperatures, but generally not more than one or two carbon atomsy lower. Also, a correspondingly higher number of carbon atoms will be required in the chain for a rise in temperature.

Representative of the foregoing plexands are the following:

2-chloro-n-tetracosane; 2-bromo-n-tetracosane; Z-amino-n-decane; Z-nitro-n-octadecane; etc.

Considering the relationships shown by Tables III and IV, it will be seen that 2-chloro-n-octadecane, for example, will form a plexad with urea at about 25 C. This, then, illustrates a plexad comprising a secondary plexand and urea. A further illustration is a non-terminal bromide such as 2-bromo-n-tetracosane-.-

By way of illustration, it follows from they foregoing that l-bromo-n-tetracosane is separated readily from a mixture of the same and anisomer such as 2-bromon-tetracosane. This is typical of a separation of a compound represented by general Formula A, above, separated from a compound represented by general Formula B, above, wherein the halogen atoms and the number of carbon atoms thereof are the same.

A further illustration stemming from the foregoing data is the eicient separation of 1chloronoctadecane from a mixture of the same and 2chloronhexadecane; or a mixturey of the same andl 2-chloro-n-cosane thus demonstrating the separation of a compound represented by general Formula A, above, from a compound represented by general Formula C:

wherein the sum of r-l-m is other than n-Z, and wherein the halogen atom is the` same as in (A).

As mentioned earlier, two paraffin derivatives of the same chain length but havingy dilferent substituents can be separated by plexation. This feature isA illustrated by selective plexad formation of 1-chloro-n-octane in a mixture containing the latter andl 2bromonoctane. This may be referred to as the separation ofa-monohaliderepresented by general Formula A from a monohalide represented by general Formula D:

wherein the sum of r-i-m is equal ton-2, andwherein the halogen atom X is different from X in (A).

Still another separation which is effected readily is that of l-chloro-n-octane from amixture containing the same and Z-brOxnO-n-heptane-or a mixture of the same and 2- bromo-n-nonane, that is, wherein the number' of carbon atoms and the halogen atoms are different. 'I'his is the separation of a compound represented by general Formula A from a compound represented by general Formula E:

wherein the sum of r-l-m is other than n-2 and wherein the halogen atom X is different from X in (A).

(2) Antiplex An antiplex, as defined above, is a compound incapable of forming a plexad with a plexor, such as urea.

(3) Plexor The plexor used herein is urea, which is in solution in a singleor multiple-component solvent. This solution should range from partially saturated to supersaturated at the temperature at which it is contacted with a plexand or with a` mixture containing` one or more plexands and antiplexes, and, in many cases, it will be found convenient to suspend a further supply of urea crystals in the solution, handling it as a slurry. For gravity or centrifugal separation, it is convenient to use a solvent of such` aspecific gravity that after the formation of a desired amount of plexad, the specic gravity of the solvent phase will be different from that of the plexad phase and of the antiplex phase to a degree sufficient to permit separation by gravity, centrifuging, etc.

The. solvent should be substantially inert to the plexand and to the compounds of the mixture and'al'so to the urea. Preferably, it should also be heat stable, both alone and in contact with urea, at temperatures atk which the desired plexad is not heat stable.

As indicated above, the solvent may be either singleor multiple-component. It is sometimes convenient, particularly where the plexad is separated by gravity, to utilize a two-component system, as water and an alcohol, glycol, amine or diamine, and preferably a lower aliphatic alcohol such as methanol or ethanol, or a water-soluble amine such as piperidine. Such a solvent, partially saturated to supersaturated with urea, lends itself readily to a continuous process for separation by plexation.

Solutions containing sufficient water in order to minimize the solubility of the hydrocarbon derivatives in the urea solvent are often employed. The minimum quantity of water required in such instances depends upon the polarity and` the molecular weight of the hydrocarbonV derivative, or plexand, being treated and, in general, this quantity will be greater with more polar plexands and with lower molecular weight compounds.

In certain cases the use of single-component solventsv is advantageous. Single-component solvents other than alcohols may be employed, although they are normally not as useful as the lower aliphatic alcohols. Glycols may be employed as single solvents, yet ethylene glycolis generally not suitable in gravity separation operations due to the high density of the urea-saturated solvent. The higher glycols and particularly the butylene glycols may be advantageously employed. Diamines such as diaminoethane, -propane and -butane may likewise be employed. Additional useful solvents include formic acid, acetic acid, formamide and acetonitrile, although the rst three of these are subject to the same limitations as ethylene glycol;

Solvents generally useful when mixed with sucient water, ethylene glycol or ethylene diamine, to render them substantially insoluble in the derivatives being treated, are selected from the class of alcohols such as methanol, ethanol, propanol, etc.; ethers such as ethylene glycol dimethyl ether; and amines such as triethylamine, hexylamine, piperidine. When gravity separation is employed, the mixed solvent is preferably subject to the restriction that the density after saturation with urea must be less than 1.0-1.1.

(4) Typical separations Inorder that this invention may be more readily understood,ltypical separations are described below with reference being made to the drawings attached hereto.

9. (a)` Separation of plexand )from antplex.-The procedure which may be employed i'n effecting, the' separation of terminally-substituted. from non-terminally substituted, straight chain hydrocarbons may be essentially the same as that described in copen'di'ng application Serial' No. 4,997, tiled January 29, 11948. Theplexand obtained in decomposingthe plexad` obtained' irra urea` treatment of a mixture of terminally-substituted and* non-terminallysubstituted, straight chain hydrocarbons is very pure, provided the substituent group and the aliphatic chain length are of suchdi-rnensions that only the terminally-substituted hydrocarbon forms a plexad and provided the plexad be carefully freed. of occluded antiplex before. it is-l decom.- posed. For example, substantially pure l-ha-lide is separated from the plexad obtained inthe treatment of termi-` nally-substituted andi non-terminally-substitutecl chlorides or bromides of normal paraftns contai-ningfromL 8-1^6-car bon atoms.

In Figure l, a charge comprising a plexand and' an antiplex, for example l-bromo-n-octane and.` 2lbrorno-noctane, respectively, entersthrough line,` lf, tobe contactedi with urea solution from line 2, and the charge and' solution are intimately mixed in mixer 3. In case the charge undergoing treatment is rather viscous. atv the temperature of plexad (l-bromo-n-octane-urea); formation, it4 is. adi' visableto provide a diluent, such as for example-anaphtha cut which may be recycled within the process, as; described later, and joins the charger fromline 4:. Diluent make up is provided by line 5..

From mixer 3,l wherein, there? is achieved: an. intimate mixture of urea` solution, and charge, the mixture hows through line 6, heatexchanger '7.,V and cooler' 81 into settler 9. There may be some or a good; portion` of plexad. (l-bromo-n-octane-urea.) formed; in mixen, but in gen1- eral, it is preferred to operate mixen at, a. temperature somewhat above that conducive to heavyy forrrrationof plexad. Then, in heat exchanger?` 7;, the temperature of the mixture. is reduced;` and in. cooler; 8f adjustedso; that, the desired plexad is formed.l It willA be recognized that, thisV showing is diagrammatic,A and that the heat: exchangers and coolers, heaters, etc., shownl will be; of any,Y type suitable as determined by the physical characteristics of the materials being handled.

From cooler 8, the `plexad-containing mixture ows into settler 9. This settler ispreferably so managed that there is an upper phase of antiplex (.Z-bromo-n-octane), an intermediate phase of urea solution, and a lower region containing a slurry of plexad in the urea solution. The incoming mixture is preferably introduced into the solution phase, so that the antiplex (2-brom`o-n-octane) may move upward and plexadv downward, through some little distance in the solution, to permit adequate separation of plexad from antiplex and antiplex from plexad.

Antiplex will be removed from settler 9 by lline 10 and introduced into fractionator 1'1, wherein the diluent is removed, to pass overhead byvapor line 12 andeventually to use through line 4. Recovered antiplex (Z-bromo-noctane) passes from the system through line 13:.V Obviously if no diluent be used,` fractionator 11 will be, dispensed with.

Plexad and urea solution, withdrawn fromA settler, 9 through line 14, are passed through. heat exchanger 7 and heater 15 to enter settler 16 through line 17; In this operation, the temperature is so adjusted that the plexand (l-brorno-n-octane) is freed from the plexad and,y in settler 16, the plexand rises to the top to be recovered from the system by means of line 18. The ureav Solution, thus reconstituted to its original condition by return to it of that portion of the urea which passed into plexad,` is withdrawn from settler 16 hy line 2 and returned to process. Naturally, in a process of, this kind there are minor' mechanical and entrainment losses of urea solution, etc., and urea solution makeup is provided for by line 19.

In many cases, the separation of, plexad and solution from antiplex may be conducted with greater facility in a centrifuge operation. Such a setup is shown.v in Figure 2', wherein only the equivalent of that portion of Figure l', entering about settler 9 is reproduced. Again in diagram form, the cooled mixture containing antiplex, plexad and urea solution enters centrifuge 20 through line 6. In many cases, it will` be desirable to utilize a carrier liquid in known manner in this operation and that liquid may be introduced by line 21. Antiplex will be carried olf through line 10, and plexad, urea solution, and carrier, if present, pass through line 22 to a separation step, which may include washing and may be carried out in a settler, a filter, or another centrifugal operation, which separation. isV indicated diagrammatically at 23. Carrier liquid, if used, returns through line 24, and urea solution and plexad pass through line 14. (Note: Lines 6, 10 and 14 are the same lines, for the same functions, as in Figure 1 'and are identically numbered).

(b) Separation of one plexand from a second plexand.-In the case where both the terminally-substituted and non-terminally-substitutedcompounds form plexad's, a concentration of the terminally-substituted compound will be obtained. The sharpness of separation of the terminally-substitutedl compound will be greater, the greater the difference in the strength of the plexads formed withthe two types of' pure compounds. greater, the shorter thecarbon chain length of parenthydrocarbon. For example, substantially pure l-bromon-octanel can be obtained froma mixture with Z-bromo-noctanein a single plexation. It is` more dilhcult, however, to obtain separation between l-chloro-n-octadecane and' 2-chloro-n-octadecane.

The following serves to illustrate a procedure for obtaining sharp separation between one plexand, lf-chl'oron-octad'ecane, and? a second plexandl, 2-chloro-n-octad'ecane, the latter behaving as asecondaryplexand' in forming a plexad. This procedure is similar to a sweating or a solvent sweating procedure used inthe reiini-ng of slack waxes, and is shown diagrammatically in Figure 3.

In Figure 3, a slurry of solid' urea ina saturated urea solvent, which isprefenably an aqueous alcoholic solution, is pumped from line 311 into` a turbomixer'32 where it is afgitated with a mixtureA of land 2-chloro-n-octadecanes, which enter through line 33. An immiscible solventl charged' through line 34.is also preferably employed, such as alight cutr from a straight' run naphtha in casethe compounds ofthe mixture treatedv have: (l1) arelatively high viscosity; (2) any appreciable solubility in the urea. sol.

vent; or (f3f)\ greater densityv than the urea solvent. The amountv of excess solid urea employed should be sufiicient so that after the plexation is completed the urea solvent remains substantially saturated with urea.

Internal Cooling means may be employed in 32 to fur-I thercool the. mixture and remove the heat evolved during'the plexation. The temperature employed in 32 will depend upon the chain length of the plexand' and seconda-ry plexand. If the chain length is such that it is not more than one or two carbon atoms greater than the minimum required to'. obtain; plexation with thel pure plexa-nd at 25 6;, then temperaturesL in the range of 10 to- 20' C. should be employed. If the chain length is from two to six carbon atoms greater than the` minimum, temperature in` the range of 1'5-30'` C. should be employed; and if the chain length is greater than six carbon atoms beyond the minimum, temperatures from 25-50 C. may be ernployed'. It will be apparent, then, that conditions of operation vary considerably, conditions selected being those appropriate for the forni'ation of the desired plexad or plexads.

The slurry of plexad,l urea solventand secondary plexand is pumped, by means of pump 36v through line: 3:5l and cooler 37 whereinit may be further cooled if desired, and into gravity settler 3S. In. settler 38 the secondary plexand plus naphtha solvent rises to the top and is withdrawn through line 39 into fractionator 40. "Ehe secondary, plexand, predominantly 2-choloro-n-octadecane, is-,re-

In general, this will be 1 1 moved as bottoms from fractionator 40 through line 4i. The naphtha solvent is taken from fractionator 40 through line 42, cooler 43, tank 44 and line 45 to be employed in solvent sweating zone 46. Naphtha solvent may also l2 resulting precipitate. The results are summarized in Table V, below, and the minimum chain length required for plexation found experimentally is compared with the correlations given in Table IV. Table V is as follows:

TABLE V.-COMPARISON OF MINIIMUM CHAIN LENGTHS REQUIRED FOR UREA ILEXA- TION AT C. FOR HYDROCARBONS-l DETERMINED EXPERIMENTALLY 'WITH THOSE GIVEN IN TABLE II. PLEXAD FORMATION-ALIPHATIC CHAIN LENGTH Group No.

Length Table II -N H2 thienyl be recycled to fractionator through line 47, by means of pump 48.

In settler 38, the slurry of plexand in urea solvent is taken olf through line 49, heat exchanger and heater 51 into solvent sweating Zone (or mixer) 46. A portion of the clear urea solvent may be removed from the center of 38 and recycled, through line 51 and pump 52, to mixer 32 if desired.

It is to be understood that the gravity settler 38 may be replaced by other separation means such as a centrifuge or rotary filter, etc.

The mixture of solvent and plexad is heated in solvent sweating zone 46 to a temperature suicient to decompose the major portion of the plexad of the 2-chloro-n-octadecane, while preserving the major portion of the plexad of 1chloronoctadecane. The temperature employed in zone 46 is related to that employed in mixer 32, and will generally be maintained from 1020 C. higher in zone 46 than in mixer 32.

The partially decomposed plexads, urea solvent, and naphtha mixture is passed from Zone 46 through line 53 to settler 54. The naphtha containing plexand, l-chloron-octadecane, and some secondary plexand, 2-ch1oro-noctadecane, is recycled through lines 55 and 33 to mixer 32. The slurry of undecomposed plexad is withdrawn from the bottom of settler 54 through line 56, heat exchanger 57, heater 58 into settler 59. The plexad is thus heated hot enough to cause complete decomposition or reversion of the plexads and solution of the urea in the urea solvent. Temperatures in the range of 55-85 C. are generally suitable.

Plexand, naphtha which had been occluded on the corresponding plexad (1-chloro-n-octadecane-urea) is withdrawn through line 60 into fractionator 61. Naphtha is taken of overhead from fractionator 61 through line 62, cooler 63, tank 64, pump 65 and line 66, to mixer 31. A portion of the naphtha may also be recycled to fractionator 61 through line 67. Plexand is recovered as bottoms through line 68.

Urea solution is recycled from the bottom of settler 59 through line 69, pump 70, heat exchangers 57 and 50, and line 51.

Plexand of any desired purity may be obtained by either: l) increasing the fraction of the total plexad decomposed in the solvent sweating Zone 46, or (2) including a multiplicity of alternating solvent sweating zones 46 and settling Zones 54 operated in series.

VII. ILLUSTRATIVE EXAMPLES The following examples serve to illustrate, and not in any sense limit, the present invention.

(a) T terminally-substituted straight chain parajjins. General Formula A.A number of such parain derivatives of varying chain length were agitated for several hours with water or with aqueous methanol solutions saturated with urea, and plexad formation was evidenced by It will be noted from the data set forth in Table V that, in all instances, experimental values found for the minimum chain length are within the limits specified in Table II.

(b) Comparison of equilibrium values in the plexation of compounds of General Formula A and B.-Plexation of a plexand, dissolved in an antiplex such as a suitable branched chain hydrocarbon solvent, with a saturated urea solution proceeds until the concentration of the plexand is reduced to a certain minimum concentration which may be termed the equilibrium concentration. In general, the equilibrium concentration is lower, the lower the temperature of plexation and is dependent only upon the temperature and not upon the solvent for the plexand, provided the urea solution is maintained saturated with urea and provided the plexand-solvent phase can be regarded as an ideal solution.

Equilibrium values were determined for several pairs of compounds, (A) and (B), by agitating solutions of varying concentrations of the substituted hydrocarbon in isooctance with a methanol-30% water solution saturated with urea and noting the minimum concentration required for plexad formation. The results are summarized in Table VI, below.

TABLE VI.EQUILIBRIUM VALUES IN THE URE/l PLEX- ATION OF HYDROCARBON-l, HYDROCARBON-Z PAIRE From the data shown in Table VI, it will be noted that the terminally-substituted compound, (A), forms a plexad, while the non-terminally-substituted compounds, (B), do not form plexads. When the compound (B) does not form a plexad, relatively sharp separation can be obtained between compounds (A) and (B) in a single plexation.

(c) Separation of J-bromo-n-octane and 2br0mo1z octane.-The following solution was contacted with urea, in a reaction vessel: equal parts by volume of l-bromo-noctane, 2-bromonoctane and 2-methy1 pentane. A portion, 45 parts by volume, of this solution was agitated at room temperature (25 C.) with 50 parts by volume of an aqueous methanol solution saturated with urea at 45 C. A plexad was formed and settled to the bottom of the urea solution. The upper layer, free of plexad, was decanted from the lower layer. The upper layer was distilled whereupon 2-rnethyl pentane was distilled off,

and the composition of the bromide residue was determined by refractive index measurement. v

The plexad was iltered from the urea solution, washed with 2methyl pentane and then decomposed with water to urea and plexand. The recovered plexand was distilled to remove 2-methyl pentane and the residue was analyzed for the bromo-octanes by refractive index.

No 2-bromo-n-octane was removed from the original solution, while the bromo-n-octane content was reduced from 33.3 volume per cent to its equilibrium value, namely, 18.7 volume percent.

VIII. UTILITY From the foregoing description, it will be apparent that the invention has considerable application in the chemical and related arts. For example, terminally sulfonated parafns may be separated from the nonterminally substituted compounds in the manufacture of detergents and wetting agents by the sulfochlorination of paraffns. This makes possible purer and more etlicient detergents and wetting agents. Similarly, l-chloro straight chain parafns may be separated from the corresponding non-terminally substituted chloro compounds, which are formed in the chlorination of straight chain paraiins. Also, in the high temperature, vapor-phase chlorination of olens, two principal products are produced, namely, the 1-chloro-2-olen and the 3chloro 1olen according to the following representation:

The present method may be employed to effect the separation between the foregoing l-chloro and the 3-chloro compounds.

The addition of a mercaptan or hydrogen bromide to a l-olefin in the presence of air, oxygen or peroxides takes place with the addition of the mercapto radical, -SR, or bromo radical, -Br, to the terminal carbon atom of the olefin. If an olefin mixture containing a straight chain l-oletin is so treated, the derivatives obtained from the straight chain l-olen can be selectively separated by urea plexation. The 1-o1etin derivatives obtained in this manner may be used for various purposes, or can be converted by known reactions to other useful products. For example, the bromide may be pyrolyzed to regenerate the pure l-olen.

Not only are the separation procedures contemplated herein useful for removing substantial amounts of a contaminating constituent, as an isomer or isomers, from a related compound, but they are of value when small or trace amounts of such an undesirable constituent are present.

In addition, the new plexads made available herein constitute desirable sources of urea and of the various plexands associated therewith. For example, the desired compounds can be kept in storage or shipped until just prior to use, when they are separated by reversion of the plexads.

Compounds characterized by a nitrogen-containing substituent are also plexated from mixtures containing the same and form plexads with urea, as described above; this subject matter is also described and is claimed in 14 i application Serial No. 115,515, now Patent No. 2,681,332, issued June 15, 1954. Sulfur-containing compounds are also plexated from their mixtures, and form plexads with urea, as described above and as described and claimed in application Serial No. 255,943, filed November 13, 1951 (now Patent No. 2,681,336, issued June 15, 1954) as a continuation of application Serial No. 115,516 which has been abandoned. Plexation of compounds containing cyclic substituents, and urea plexads thereof, are described and are claimed in application Serial No. 116,593 (now Patent No. 2,681,334, issued June 15, 1954), in the same manner as described above. Plexation with urea of various terminally substituted compounds from mixtures containing the same and nontermnally substituted compounds, described above, is also described and is claimed in application Serial No. 115,517, now Patent No. 2,681,333, issued June 15, 1954.

Urea plexation of a non-terminally mono-substituted compound from mixtures containing the same and a non-terminally poly-substituted compound is described and is claimed in application Serial No. 115,513, now Patent No. 2,642,422, issued June 16, 1953. Urea plexation of mixtures containing aliphatic compounds of different degrees of unsaturation is described and is claimed in application Serial No. 115,514, now abandoned; similarly, plexation of mixtures containing aliphatic hydrocarbons of different degrees of unsaturation and urea plexads of such hydrocarbons, are described and are claimed in application Serial No. 115,518 (now Patent No. 2,642,423, issued June 16, 1953) and in divisional application thereof Serial No. 266,547, filed January 15, 1952.

Said applications Serial Nos. 115,513 through 115,518 and 116,593 were Vtiled on September 13, 1949.

I claim:

1. Crystalline complex of urea and a straight chain alkyl monohalide consisting of carbon, hydrogen and halogen, and having the halogen atom thereof joined to other than a terminal carbon atom of the chain, said monohalide being selected from the group consisting of a fluoride having at least seven carbon atoms in the chain, a chloride having at least eighteen carbon atoms in the chain, a bromide having at least twenty carbon atoms in the chain, and an iodide having at least twentyfour carbon atoms in the chain.

2. Crystalline complex as deued by claim 1 wherein said monohalide is a fluoride.

3. Crystalline complex as defined by claim 1 wherein said monohalide is a chloride.

4. Crystalline complex as defined by claim 1 wherein said monohalide is a bromide.

5. Crystalline complex as dened in claim 1 wherein said monohalide is an iodide.

References Cited in the le of this patent UNITED STATES PATENTS 2,520,715 Fetterly Aug. 29, 1950 2,557,257 Melrose June 29, 1951 2,569,984 Fetterly Oct. 2, 1951 2,642,422 Gorin June 16, 1953 2,681,333 Gorin June 15, 1954 2,702,289 Bowman et a1 Feb. 15, 1955 

1. CRYSTALLINE COMPLEX OF UREA AND A STRAIGHT CHAIN ALKYL MONOHALIDE CONSISTING OF CARBON, HYDROGEN AND HALOGEN, AND HAVING THE HALOGEN ATOM THEREOF JOINED TO OTHER THAN A TERMINAL CARBON ATOM OF THE CHAIN, SAID MONOHALIDE BEING SELECTED FROM THE GROUP CONSISTING OF A FLUORIDE HAVING AT LEAST SEVEN CARBON ATOMS IN THE 